The effective mass, vibration and electromagnetic properties of tetragonal iron aluminide FeAl2

Abstract

MoSi2-type tetragonal iron dialuminide (space group I4/mmm) have been successfully synthesized and determined in a previous stud by Tobita et al. In this work, the electronic structure, effective mass, vibration, and electromagnetic properties of t-FeAl2 were predicted using the density functional theory (DFT). First, the predicted crystal lattice parameters reproduced the previously reported experimental data. Second, the electronic structure shows that t-FeAl2 is a narrow-gap semiconductor material with an indirect gap (0.059 eV), and the effective masse of the electron (me*) and hole (mh*) is 0.35 m0 and 0.2 m0, respectively. Third, the electromagnetic wave absorption characteristics such as the frequency-dependence of the relative complex permittivity, dielectric loss tangent tgδ, electrical conductivity, quality factor Q × f and reflection loss are calculated. Besides, using the linear response theory, the phonon dispersion curves and vibrational properties are calculated. The phonon dispersion curves do not have imaginary phonon frequencies, confirming the dynamic stability of t-FeAl2. Finally, the vibrational properties are investigated, and the infrared (IR)-active and Raman-active modes are also assigned and briefly discussed.